Thanks for your help.
I chose “reset app” / “Renew app” and rebooted my system. Unfortunately the same problem remains when I start MSFS.
I seem to be able to log in normally when I use the XBOX live (url) page.
However, when I choose the X-Box app from within the Windows Startmenu I get conflicting information…
So far all looks normal although I don’t seem to be logged in.
When I click the “sign in” option in the upper left corner I get the option “change settings”.
When I select “login” in the next window I see another login window…and again a login option.
When I select the option “login” in this window an ‘error message’ pops up saying I can’t login due to an ‘unexpected error’.
Thanks again for your suggestions. I hope I overlooked something simple.